1. Field of the Invention
The present invention is related to an improved method for atomic layer deposition. Further, it is also related to a reactor design suitable for applying the method.
2. Description of the Related Technology
Because in the field of electronics in general further downscaling of the semiconductor devices is always proceeding, deposition processes have to be developed able to deposit layers with a thickness control at atomic layer scale.
One of these deposition techniques is atomic layer deposition (ALD), often used for depositing dielectric layers.
Atomic layer deposition is a thin film deposition technique based on the used for separated chemisorption reactions of at least two gas phase reactants with a substrate.
There are two characteristics which can limit the quality and scalability of layers deposited by ALD. A first characteristic is the growth-per-cycle (GPC), which often is much lower than the theoretical maximum of one monolayer per cycle. This can result in film roughness and slow film closure, which makes especially thin films (thinner than about 5 nm) prone to localized defects such as pinholes.
A second characteristic is the presence of impurities due to unreacted precursor ligands.
For example, in the deposition of hafnium oxide from hafnium tetrachloride and water, the growth-per-cycle is only 20% of a monolayer and the Cl-impurities remain in the deposited layer.